Surveying the Deflection of an Arch Bridge to Sub-millimetre Precision

This paper describes a survey of an engineering structure that required high precision results. It is intended as a case study, primarily for surveying students, though the application of the techniques may provide insight to a wider audience. The purpose of the survey was to monitor movements of a new arch bridge to better than ±1 mm. The coordinates of targets placed on the arch structure were not required, only deflections between subsequent epochs of measurements were required. Our survey procedures provided arch deflections in the vertical direction to better than ± 0.4 mm and in the in-plane direction to ± 0.8 mm.